He continued: "I think that what Rudy has done is a shame and a disgrace as a former USA attorney, and as a former justice official, he knows better, and it's an outright lie".

Senate Majority Whip John Cornyn, who also serves on the Judiciary Committee, told Business Insider that Trump's opinion "may be right from a strictly legal standpoint, but I don't think it's helpful in terms of the conclusion of the investigation".

The talk of self-pardoning has raised eyebrows amid the roiling debate over the Russian Federation meddling inquiry and the president's cooperation - or lack of it. Trump has issued a series of ever-sharper tweets attacking the Mueller probe as politically motivated and insisting there was "no collusion" between his campaign team and Russian Federation.

Giuliani said Kim quickly changed his position, expressed willingness to discuss denuclearization and asked to have the meeting again. "Despite that, we play the game because I, unlike the Democrats, have done nothing wrong!" - he initially wrote.

Trump's legal team has also argued that the president shouldn't have to answer any questions, even if Mueller issues a grand jury subpoena, citing Trump's executive authority.

Trump did not detail his grounds for claiming that the Mueller investigation is illegal.

"It violates constitutional prohibitions on self-dealing, and if you use the pardon power to eviscerate checks on the presidency, that's also an abuse of the pardon power", Gillian Metzger, a constitutional-law scholar at Columbia University told the daily.

Trump's lawyers don't want him to be interviewed by Mueller, accusing the independent prosecutor, himself a former Federal Bureau of Investigation chief, of trying to "trap" the president in a lie.

Giuliani said that impeachment would be the remedy for a president's illegal behavior, offering as an example the hypothetical case of Trump shooting Comey rather than firing him, the HuffPost reported.

Lifestyle guru and businesswoman Martha Stewart is on the list of new potential pardons - though a source said the president has cooled on that idea. The President has never said he pardoned himself.